Fabrication and characterization of Ag-doped Li_1.3Al_0.3Ti_1.7(PO₄)₃ solid electrolyte with high ionic conductivity

Lithium superionic conductor (LISICON) Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP) is known as a high lithium-ion conductive solid electrolyte. The top-down approach was utilized in this work to synthesize LATP in which Ag with concentrations of 1, 2, 4, 6, 8 wt% was incorporated in the host material and the performance of the fabricated solid electrolyte was examined and compared with that of the pristine material. Substitution of Li⁺ by Ag⁺ in LATP structure resulted in bulk conductivity of 1.1 × 10^–3 S cm⁻¹ and grain boundary conductivity of 1.0 × 10^–3 S cm⁻¹ at 25 °C for the optimum Ag concentration of 4 wt%. The calcination process was performed in several temperature steps to prevent the release of volatile substances. To obtain a pure LATP structure, phase analyses were performed using X-ray diffraction (XRD) patterns to improve the synthesis conditions. High density, low unwanted and amorphous phases and increased ionic conductivity were achieved by applying sintering process and optimizing the amounts of additives. Effective surface area of about 16 g m⁻² was measured using Brunauer–Emmett–Teller (BET) analysis. Negligible decomposition of the products was observed by employing thermal analyses (TGA/DSC). The bulk conductivity of the fabricated solid electrolyte is among the highest reported bulk conductivity for LATP and the grain boundary conductivity revealed by electrochemical impedance spectroscopy (EIS) test is higher than other reported values for LATP. So, the fabricated solid electrolyte is recommended for using in electrically charged solid-state lithium batteries.